Ignition and Combustion of Aluminium in High Explosives

Arno Hahma

Abstract: Ignition and combustion properties of aluminium powder up to 250 kbar pressure were successfully determined. Hydrodynamic modelling combined with parametrized reaction profiles was used to match the experimental metal plate profiles to calculated values and the metal reactivity was determined from the parameters thus obtained. The reaction profiles over a wide range of specific volumes and pressures were obtained. Aluminium ignited only if the detonation temperature was higher than 2300 K and the aluminium oxide was decomposed; even a strong shock wave was not able to clean the aluminium surface to promote ignition at lower temperatures. Aluminium reactivity at the Chapman–Jouguet plane (C-J plane) was concluded to be insignificant in all cases studied. A maximum of only 17 % reactivity by an expansion ratio of 1 : 50 was reached. The aluminium combustion could be best described with a power law Apn and the pressure exponent of aluminium was found to be slightly positive: +0.33. Nitrogen rich explosives were concluded to be necessary to convert Al energy effectively to mechanical work and to unambiguously measure the Al reactivity.

Keywords: Aluminium, Chapman–Jouguet plane, ignition, combustion, hydrodynamic modelling

Ref: JPyro, Issue 26, 2007, pp24-46

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